Effectiveness of Remotely-Sensed Lineaments and
Outcrop-Scale Fractures in

Identifying Bedrock Aquifers in New England

Duration: 9/96 to 9/98

Federal Funds Requested: $38,018

Non-Federal Matching Funds Pledged: $76,404

Principal Investigator: Stephen B. Mabee, University of
Massachusetts

Congressional District: 1 st Congressional District

Project Summary

The spatial extent and physical characteristics of
bedrock discontinuities are primary factors controlling the storage and
movement of groundwater in fractured rock. Obtaining a firm grasp of the
three-dimensional geometry and hydrology of fracture networks is critical to
understanding contaminant transport, designing effective remediation, or
developing new water supplies. However, most of what is known about the
fracture network in the subsurface comes from observations made at surface
outcrops or in a few well-placed boreholes. It is a rare occurrence when
researchers can make direct, "first-hand', observations from within the
rock mass.

The Massachusetts Water Resources Authority is
constructing a new water supply tunnel through eastern Massachusetts beginning
in the summer of 1996. The 28 km-long tunnel will traverse three accreted
geologic terranes at an average depth of 70 m below ground. This will provide a
unparalleled opportunity to make detailed observations of fracture features and
groundwater flow conditions in the subsurface. Measurements made in the tunnel
will provide a unique database of fracture information against which surface
geophysical, borehole, geochemical, remotely-sensed lineament and outcrop-scale
fracture data can be rigorously compared.

The purpose of this proposed research is to: 1 ) document
the location, orientation, physical characteristics, and approximate yield of
water-beating discontinuities within an initial, 10-15 km section of the
tunnel; and, 2) use these measurements to; a) assess the reliability of using
remotely-sensed lineaments to predict zones of high groundwater yield within
the bedrock, and, b) compare the geometry and physical characteristics of
fracture features observed in surface outcrops with those observed in the
tunnel. Results of this work will not only quantify the relationship between
lineaments and subsurface fractures but will also evaluate whether or not
fracture characteristics observed in surface outcrops can be extrapolated into
the third dimension with any degree of certainty. The University of
Massachusetts has already obtained permission to access the tunnel during the
entire 5-year construction phase.

Statement of Regional Need for Research

Growth and development in the northeast arc placing high
demands on groundwater resources. Many of the areas experiencing this growth
rely on bedrock wells to meet potable water supply demands, particularly in
rural New England communities. For these reasons, bedrock aquifers are
considered important and areas possessing high-yield potential must be
identified and protected. However, planners, state agencies, and individuals
who must make decisions regarding aquifer management and protection or who must
establish siting criteria for landfills and other water quality-threatening
facilities need guidance in identifying and evaluating important bedrock
aquifers.

Lineament analysis of remotely-sensed imagery remains one
of the most commonly used reconnaissance tools for assessing potentially
transmissive zones in the bedrock. The technique used for both region-wide
studies and small-scale site investigations. However, the method is inherently
subjective (Siegal, 1977; Podwysocki and others, 1975; Wise, 1983a) and
certainly not all lineaments guarantee finding highly transmissive
discontinuities in the bedrock. Despite these shortcomings, the method
continues to be used by hydrogeologists even though no significant advancements
have been made to improve the predictive capability of lineament analysis since
the connection between lineaments and groundwater was first established by
Lattman and Parizek (1964). The fundamental problem with the lineament analysis
technique is that no one has been able to associate lineaments with specific
water-beating fractures in the subsurface. This project will provide a unique
opportunity to acquire tangible evidence from the subsurface that will quantify
the relationship between lineaments and water-bearing discontinuities in the
bedrock. It will also provide an opportunity to explore some of the other
geologic factors that may influence, as well as improve, the predictive
capability of the method.

Statement of Regional Benefit From the Results of this
Project

Direct benefits expected as a result of this research
project include: 1) verification of the reliability of the method as a tool for
predicting high-yield fracture zones in the bedrock; 2) quantification of some
of the other geologic factors that may control the usefulness and reliability
of the method as a predictive tool, for example, structural setting, bedrock
type, proximity to surface water bodies, type and thickness of overburden,
fracture characteristics such as spacing, planarity, trace length, etc.; 3)
development of a framework for cataloguing lineament and fracture data on a
regional scale; and 4) development of a lineament mapping protocol for
delineating possible high-yield fractured-bedrock aquifers on a state or
regional level.

Regional planners, state agencies and other individuals
will be given a methodology that will allow initial preparation of maps and
overlays indicating the location of important bedrock aquifers. These maps,
which can easily be incorporated into GIS applications, will provide planning
guidance for remediation programs, aquifer management and protection, and
siting criteria for facilities and land uses that may threaten groundwater
quality. Although this project is situated in Massachusetts, the results will
benefit, in particular, the entire New England area since this region shares a
common geologic heritage and shares the same desire to identify bedrock
aquifers with greater reliability.